Graphene’s germanium cousin holds promise for energy-efficient electronics

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Researchers from the University of Twente have proven that germanene, the germanium equivalent of graphene, behaves as a topological insulator. It’s the first 2D topological insulator that consists of a single element. It also has the unique ability to switch conduction ‘on’ and ‘off.’ This could lead to more energy-efficient electronics.

Topological insulators are materials with the unique property of insulating electricity in their interior while conducting electricity along their edges. The conductive edges allow electrical current to flow without energy loss. “At the moment, electronic devices lose a lot of energy in the form of heat because defects in the material increase the resistance. As a result, your mobile phone can get uncomfortably hot,” explains UT researcher Pantelis Bampoulis.

Scanning tunneling microscopy topography of germanene’s honeycomb lattice. Credit: University of Twente

Due to the unique nature of topological insulators, scattering of electrons doesn’t occur and therefore electrical current in 2D topological insulators flows without dissipating energy. This makes them more energy-efficient than current electronic materials.

Previously known topological insulators consist of complex mixtures from different types of elements. “Germanene is unique in that it’s made from just a single element,” says Bampoulis. To create this exciting material, the researchers melted germanium together with platinum. When the mixture cooled down, a tiny layer of germanium atoms formed a honeycomb lattice on top of the germanium-platinum alloy.

The researchers also discovered that the conducting properties of the material can be switched ‘off’ by applying an electric field. This property is unique for a topological insulator. “The possibility to switch between ‘on’ and ‘off’ states adds an exciting application case for germanene,” notes Bampoulis. It paves the way for designing topological field-effect transistors. Chips based on these electronic switches wouldn’t heat up.

Electrons also zip easily through graphene’s lattice, but lacking an intrinsic bandgap, it has to be engineered.